[red-knot] Stabilize `negation_reverses_subtype_order` property test (#16801)

## Summary

This is a re-creation of https://github.com/astral-sh/ruff/pull/16764 by
@mtshiba, which I closed meaning to immediately reopen (GitHub wasn't
updating the PR with the latest pushed changes), and which GitHub will
not allow me to reopen for some reason. Pasting the summary from that PR
below:

> From https://github.com/astral-sh/ruff/pull/16641
> 
> As stated in this comment
(https://github.com/astral-sh/ruff/pull/16641#discussion_r1996153702),
the current ordering implementation for intersection types is incorrect.
So, I will introduce lexicographic ordering for intersection types.

## Test Plan

One property test stabilised (tested locally with
`QUICKCHECK_TESTS=2000000 cargo test --release -p
red_knot_python_semantic -- --ignored
types::property_tests::stable::negation_reverses_subtype_order`), and
existing mdtests that previously failed now pass.

Primarily-authored-by:
[mtshiba](https://github.com/astral-sh/ruff/commits?author=mtshiba)

---------

Co-authored-by: Shunsuke Shibayama <sbym1346@gmail.com>

crates/red_knot_python_semantic/resources/mdtest/type_properties/is_gradual_equivalent_to.md

@@ -42,8 +42,6 @@ static_assert(is_gradual_equivalent_to(str | int, int | str))
 static_assert(
     is_gradual_equivalent_to(Intersection[str, int, Not[bytes], Not[None]], Intersection[int, str, Not[None], Not[bytes]])
 )
-# TODO: `~type[Any]` shoudld be gradually equivalent to `~type[Unknown]`
-# error: [static-assert-error]
 static_assert(is_gradual_equivalent_to(Intersection[str | int, Not[type[Any]]], Intersection[int | str, Not[type[Unknown]]]))
 
 static_assert(not is_gradual_equivalent_to(str | int, int | str | bytes))

crates/red_knot_python_semantic/src/types.rs

@@ -9,7 +9,7 @@ use ruff_db::files::File;
 use ruff_python_ast as ast;
 use ruff_python_ast::name::Name;
 use ruff_text_size::{Ranged, TextRange};
-use type_ordering::union_elements_ordering;
+use type_ordering::union_or_intersection_elements_ordering;
 
 pub(crate) use self::builder::{IntersectionBuilder, UnionBuilder};
 pub(crate) use self::diagnostic::register_lints;
@@ -494,13 +494,13 @@ impl<'db> Type<'db> {
     /// Return a normalized version of `self` in which all unions and intersections are sorted
     /// according to a canonical order, no matter how "deeply" a union/intersection may be nested.
     #[must_use]
-    pub fn with_sorted_unions(self, db: &'db dyn Db) -> Self {
+    pub fn with_sorted_unions_and_intersections(self, db: &'db dyn Db) -> Self {
         match self {
             Type::Union(union) => Type::Union(union.to_sorted_union(db)),
             Type::Intersection(intersection) => {
                 Type::Intersection(intersection.to_sorted_intersection(db))
             }
-            Type::Tuple(tuple) => Type::Tuple(tuple.with_sorted_unions(db)),
+            Type::Tuple(tuple) => Type::Tuple(tuple.with_sorted_unions_and_intersections(db)),
             Type::LiteralString
             | Type::Instance(_)
             | Type::AlwaysFalsy
@@ -4945,9 +4945,9 @@ impl<'db> UnionType<'db> {
         let mut new_elements: Vec<Type<'db>> = self
             .elements(db)
             .iter()
-            .map(|element| element.with_sorted_unions(db))
+            .map(|element| element.with_sorted_unions_and_intersections(db))
             .collect();
-        new_elements.sort_unstable_by(union_elements_ordering);
+        new_elements.sort_unstable_by(|l, r| union_or_intersection_elements_ordering(db, l, r));
         UnionType::new(db, new_elements.into_boxed_slice())
     }
 
@@ -5048,10 +5048,10 @@ impl<'db> IntersectionType<'db> {
         ) -> FxOrderSet<Type<'db>> {
             let mut elements: FxOrderSet<Type<'db>> = elements
                 .iter()
-                .map(|ty| ty.with_sorted_unions(db))
+                .map(|ty| ty.with_sorted_unions_and_intersections(db))
                 .collect();
 
-            elements.sort_unstable_by(union_elements_ordering);
+            elements.sort_unstable_by(|l, r| union_or_intersection_elements_ordering(db, l, r));
             elements
         }
 
@@ -5317,11 +5317,11 @@ impl<'db> TupleType<'db> {
     /// Return a normalized version of `self` in which all unions and intersections are sorted
     /// according to a canonical order, no matter how "deeply" a union/intersection may be nested.
     #[must_use]
-    pub fn with_sorted_unions(self, db: &'db dyn Db) -> Self {
+    pub fn with_sorted_unions_and_intersections(self, db: &'db dyn Db) -> Self {
         let elements: Box<[Type<'db>]> = self
             .elements(db)
             .iter()
-            .map(|ty| ty.with_sorted_unions(db))
+            .map(|ty| ty.with_sorted_unions_and_intersections(db))
             .collect();
         TupleType::new(db, elements)
     }

crates/red_knot_python_semantic/src/types/property_tests.rs

@@ -420,6 +420,12 @@ mod stable {
         forall types s, t. s.is_subtype_of(db, t) && t.is_subtype_of(db, s) => s.is_equivalent_to(db, t)
     );
 
+    // If `S <: T`, then `~T <: ~S`.
+    type_property_test!(
+        negation_reverses_subtype_order, db,
+        forall types s, t. s.is_subtype_of(db, t) => t.negate(db).is_subtype_of(db, s.negate(db))
+    );
+
     // `T` is not disjoint from itself, unless `T` is `Never`.
     type_property_test!(
         disjoint_from_is_irreflexive, db,
@@ -546,12 +552,6 @@ mod flaky {
         forall types t. t.is_fully_static(db) => t.negate(db).is_disjoint_from(db, t)
     );
 
-    // If `S <: T`, then `~T <: ~S`.
-    type_property_test!(
-        negation_reverses_subtype_order, db,
-        forall types s, t. s.is_subtype_of(db, t) => t.negate(db).is_subtype_of(db, s.negate(db))
-    );
-
     // For two fully static types, their intersection must be a subtype of each type in the pair.
     type_property_test!(
         all_fully_static_type_pairs_are_supertypes_of_their_intersection, db,

crates/red_knot_python_semantic/src/types/type_ordering.rs

@@ -1,5 +1,6 @@
 use std::cmp::Ordering;
 
+use crate::db::Db;
 use crate::types::CallableType;
 
 use super::{
@@ -11,8 +12,9 @@ use super::{
 /// in an [`crate::types::IntersectionType`] or a [`crate::types::UnionType`] in order for them
 /// to be compared for equivalence.
 ///
-/// Two unions with equal sets of elements will only compare equal if they have their element sets
+/// Two intersections are compared lexicographically. Element types in the intersection must
-/// ordered the same way.
+/// already be sorted. Two unions are never compared in this function because DNF does not permit
+/// nested unions.
 ///
 /// ## Why not just implement [`Ord`] on [`Type`]?
 ///
@@ -20,7 +22,11 @@ use super::{
 /// create here is not user-facing. However, it doesn't really "make sense" for `Type` to implement
 /// [`Ord`] in terms of the semantics. There are many different ways in which you could plausibly
 /// sort a list of types; this is only one (somewhat arbitrary, at times) possible ordering.
-pub(super) fn union_elements_ordering<'db>(left: &Type<'db>, right: &Type<'db>) -> Ordering {
+pub(super) fn union_or_intersection_elements_ordering<'db>(
+    db: &'db dyn Db,
+    left: &Type<'db>,
+    right: &Type<'db>,
+) -> Ordering {
     if left == right {
         return Ordering::Equal;
     }
@@ -83,7 +89,11 @@ pub(super) fn union_elements_ordering<'db>(left: &Type<'db>, right: &Type<'db>)
         (Type::Callable(CallableType::General(_)), _) => Ordering::Less,
         (_, Type::Callable(CallableType::General(_))) => Ordering::Greater,
 
-        (Type::Tuple(left), Type::Tuple(right)) => left.cmp(right),
+        (Type::Tuple(left), Type::Tuple(right)) => {
+            debug_assert_eq!(*left, left.with_sorted_unions_and_intersections(db));
+            debug_assert_eq!(*right, right.with_sorted_unions_and_intersections(db));
+            left.cmp(right)
+        }
         (Type::Tuple(_), _) => Ordering::Less,
         (_, Type::Tuple(_)) => Ordering::Greater,
 
@@ -264,11 +274,44 @@ pub(super) fn union_elements_ordering<'db>(left: &Type<'db>, right: &Type<'db>)
         (Type::Dynamic(_), _) => Ordering::Less,
         (_, Type::Dynamic(_)) => Ordering::Greater,
 
-        (Type::Union(left), Type::Union(right)) => left.cmp(right),
+        (Type::Union(_), _) | (_, Type::Union(_)) => {
-        (Type::Union(_), _) => Ordering::Less,
+            unreachable!("our type representation does not permit nested unions");
-        (_, Type::Union(_)) => Ordering::Greater,
+        }
 
-        (Type::Intersection(left), Type::Intersection(right)) => left.cmp(right),
+        (Type::Intersection(left), Type::Intersection(right)) => {
+            debug_assert_eq!(*left, left.to_sorted_intersection(db));
+            debug_assert_eq!(*right, right.to_sorted_intersection(db));
+
+            if left == right {
+                return Ordering::Equal;
+            }
+
+            // Lexicographically compare the elements of the two unequal intersections.
+            let left_positive = left.positive(db);
+            let right_positive = right.positive(db);
+            if left_positive.len() != right_positive.len() {
+                return left_positive.len().cmp(&right_positive.len());
+            }
+            let left_negative = left.negative(db);
+            let right_negative = right.negative(db);
+            if left_negative.len() != right_negative.len() {
+                return left_negative.len().cmp(&right_negative.len());
+            }
+            for (left, right) in left_positive.iter().zip(right_positive) {
+                let ordering = union_or_intersection_elements_ordering(db, left, right);
+                if ordering != Ordering::Equal {
+                    return ordering;
+                }
+            }
+            for (left, right) in left_negative.iter().zip(right_negative) {
+                let ordering = union_or_intersection_elements_ordering(db, left, right);
+                if ordering != Ordering::Equal {
+                    return ordering;
+                }
+            }
+
+            unreachable!("Two equal intersections that both have sorted elements should share the same Salsa ID")
+        }
     }
 }